Your Digest for Sunday, Oct 22, 2023 08:59 PM


  1. Fragile X - the commonest form of autism of known cause.
  2. Myotonic dystrophy - #autosomalDominant

#2019BSQ-OCT/Q50
VirchowsTriad2.png


There are two types of HIV virus. HIV-1 is more virulent and causes most of the HIV infections, compared to HIV-2.Source-Wiki
HIVVirusStructure.png


📑Typhoid

[!INFO] Introduction to salmonella
Salmonellae are motile gram-negative bacilli that infect or colonize a wide range of mammalian hosts.
Salmonellae cause a number of clinical infections in humans; these include:

📑Enteric fever
📑Causative agent: Salmonella typhi AND S. Paratyphi A B and S
📑Humans are the only host of these.😔
📑Epithelium -> Peyer's patches (causing HYPERTROPHY of Peyer's patches) -> RET via lymph and blood -> Eventually, organisms reside within tissue macrophages in the liver, spleen, and bone marrow.

  1. Acute illness
    Symptoms: "stepwise" fever + chills + abdominal pain 📑5-21 days after exposure. (Not rapid like cholera )
    Rose spots are non tender, blanching papules. - occurs in 2nd week.
    Intestinal rupture (3rd week) -> ? sepsis

Investigations:

Diagnosis: Culture of organism from blood, stool, bone marrow, urine or rose spots / ELISA

Treatment: Antibiotics :

Prevention: two types of 📑vaccinations are given : live attenuated (oral) and antigen based (IM)

Nontyphoidal salmonella

#2019BSQ-OCT/33
(search Non-typhoidal salmonella)


#2019BSQ-OCT/Q32

Community associated MRSA (CA-MRSA) infection is a known entity in which patients develop MRSA infection with no contact with healthcare settings. Presents as soft tissue infections in young, healthy people.
Risk factors for CA-MRSA

Empiric coverage for MRSA is generally warranted for treatment of skin and soft tissue infections, given the high community prevalence of MRSA - UpToDate

Risk factors for infection due to HA-MRSA (Hospital acquired)

MRSA transmission:

Treatment of MRSA infections


myastheniaGravis.png
#2019BSQ-OCT/Q58

[!WARNING] Table cropped in readable length mode!!!
| #x-linked-recessive | #x-linked-recessive | #autosomalDominant ; fascioscapulohumeral is one of the commonest | #autosomalDominant , MD is the most common dystrophy among europeans | #autosomal-Recessive |
| Dystrophin present but low levels | Dystrophin absent | - | Type 1 - trinucleotide repeat, Type 2 - tetranucleotide repeat | Degeneration of cranial nerve nuclei in brain stem and anterior horn cells in the spinal cord. (I.e affects the lower motor neurons) |
| Remain ambulatory beyond 16 yo; | Death by 20 years; apparent by age 4. | Onset 10 – 40 years but normal life expectancy due to slow progression | Onset of symptoms: 20 – 50 years | From infancy to adulthood depending on severity of phenotype |
| Survive to over 30 yo; | Gower’s sign, Calf pseudohypertrophy Proximal limb weakness | Face, Shoulders, Scapular winging, Foot drop Typically asymmetrical | Distal muscle weakness, Ptosis, weakness of facial muscles and sternocleidomastoid | Diffuse, symmetrical proximal weakness, Lower limb > Upper limb Absent tendon reflexes |
| - | Myocardium is affected -> Can cause Dilated C. myopathy | May have deafness and retinal involvement. | Many systems affected: Endocrine → Small pituitary fossa and hypogonadism Frontal baldness Impaired glucose tolerance Cataracts Cardiomyopathy with conduction defects Oesophageal dysfunction | - |


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Cerebellar anatomy

Cerebellar peduncles

A wide variety of manifestations are possible. These can be remembered using the acronym ‘DANISH‘:

[!INFO] Cerebellar damage also causes
Decomposition of movement
Impairment of motor learning - no adaptation of vestibulooccular reflex.
Source

Functional anatomy

  1. Cerebrocerebellum - consists of the lateral hemispheres -> Important in coordination of visually guided movements.
  2. Spinocerebellum - Regulates body movements and receives proprioceptive information
  3. Vestibulocerebellum - consists of the flocculonodular lobe; controls balance, ocular reflexes and fixation on a target and maintenance of posture.
    cerebellumAnatomyKenHub.jpg

Thus, the inputs to the cerebellum are conveyed primarily through the inferior and middle cerebellar peduncles, whereas the outputs are conveyed primarily through the superior cerebellar peduncle Source

brainstemGlossopharyngealNerve.jpeg


| Epstein–Barr virus | • 40% of Hodgkin lymphoma • >95% of endemic Burkitt lymphoma • 10% gastric carcinoma • Most (type II and III) nasopharyngeal carcinomakaposi sarcoma • Other lymphomas (NK cell lymphomas) | • East Asia • East Africa • Regions of the Americas |

Summary of pathogenesis

#2019BSQ-OCT/Q46

HTLV is the only RNA oncovirus (which is mentioned in Robbins)

Oncogenic DNA viruses


#2019BSQ-OCT/Q46
H pylori is non-invasive.
- Gastric adenocarcinoma is promoted by production of CagA by H. pylori which has effects mimicking unregulated growth stimulation.
- Maltoma: H pylori stimulates H pylori reactive T cells which drive B cell proliferation; The lymphomas are of B cell origin.
- Early H pylori eradication "cure" the lymphoma.


#2019BSQ-OCT/Q54

The complement system consists of a set of plasma glycoproteins.Source.

What follows are several images of how the complement system works;
complementSystemOverview.pngSource

Main functions of the complement proteins

complementSystem.svg
Source

[!INFO]
complementOverview.gif
C3a is an anaphylatoxin
C3b is an opsonin (it binds to foreign molecules) -> it tags microorganisms as foreign.

Activation of the 3 complement pathways

Classical pathway

Alternative pathway

Basically, C3 is constantly being hydrolysed at low levels to form C3b but this is inactivated rapidly. If the C3b happens to bind to a pathogen, it become protected from inactivation and can trigger subsequent cascade activation.
The alternative pathway does not require antibodies.
It is triggered when C3b binds to bacterial polysaccharides and other endotoxins.

More details:

The alternative pathway of complement activation depends on spontaneous hydrolysis of C3 in plasma leading to the formation of C3 (H2O). This molecule binds to factor B. Subsequent activation by factor D results in the formation of C3 (H2O) Bb. This complex cleaves additional C3 to C3a and C3b constantly and at a low rate. In the presence of an activating surface (e.g. a bacterial wall), C3b is protected from inactivation by regulatory proteins like factor I and H. As a result, a more active alternative pathway C3 convertase - called C3bBb- is formed, which is further stabilized by properdin.Source
#2019BSQ-OCT/43


#2019BSQ-OCT/Q14


#2019BSQ-OCT/29

Cohort study

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Advantages of cohort study